The primary focus of many resistance exercise machine builders has been the design of exercise machines so that the angle of motion of these machines maximizes the machine's effect on the targeted muscle or muscles. These machines have emulated movements that target various muscles and muscle groups. They are able to apply a given resistance through a weighted plate pulley system, weighted plates with sliding tubes, U.S. Pat. No. 6,436,013, flexible material, U.S. Pat. No. 5,387,171, springs, leverage systems, hydraulic, U.S. Pat. No. 4,979,735, pneumatic, U.S. Pat. No. 4,728,101, braking systems, U.S. Pat. No. 4,822,037 and such the like—a resistance source.
Some machines have focused on providing a variable-resistance mechanism along the range of motion of the exercise being performed. Some of these variable-resistance machines use a cam with variable radii or cam profile. With this mechanism, as the cam rotates it varies the mechanical advantage the user has at different points along the range of motion. This type of mechanism is commonly associated with Nautilus type machines. Other resistance exercise machine use a weighted leverage arm (pivot-type machines).
Most resistance exercise machines, including those with the afore-mentioned variable-resistance mechanism, use a tether such as a wire cable, a chain, a belt, or the like connected to an attached resistance. This attached resistance source is itself, in most cases, adjustable so as to increase or decrease the resistance along the range of motion of the exercise being performed. The increase and decrease in resistance can easily be performed with a weight stack by placing the pin in the stack at the desired weight setting. With the more modern machines, a user merely punches in the desired level of resistance. These variable-resistance exercise machines with means for selecting the degree of resistance are common throughout the exercise machine industry.
Weight machines are also used in the rehabilitation field. In this field it is important the patient receives the benefit of resistance training over a limited or if possible a full range of motion for the given exercise. Some machines have focused on limiting the range of the exercise. These machines may be useful for rehabilitation since they may prevent further injury by limiting the range of motion, U.S. Pat. No. 5,722,921.
Other machine builders have focused on isokinetic machines. These machines focus on a constant speed with variable workload or accommodating resistance. With these machines the user is forced to perform the exercise along a range of motion within a given time frame. These machines are kinetic in nature and do not provide for isometric exercise.
All of the afore-mentioned machines and those heretofore known do not focus on exercising the muscle or muscles isometrically and forcing the muscle or muscles to overcome inertia during and along the range of motion of an exercise being performed and thus do not focus on isometric and incremental muscle contraction during a repetition.
The benefits of resisted muscle contraction exercises and isometric exercise have been known. Isometric and resisted muscle contraction has been shown to induce muscle hypertrophy and increase muscle growth factors (Skeletal muscle hypertrophy in response to isometric, lengthening, and shortening training bouts of equivalent duration. J Appl Physiol. May 2004; 96(5):1613-8.). However, there is no exercise machine designed for the user to perform an isometric and incremental contraction or an incremental and isometric contraction along the range of motion of the exercise performed.
Thus, there remains a need for an exercise apparatus that works the targeted muscle or muscle groups isometrically and concentrically during and along a range of motion of an exercise being performed on the exercise apparatus.